sharks are color blind right? and it's really the contrast they're drawn to (like the dark blob of a seal from below—or a surfer), but i'm just not seeing how this mitigates that. i want to believe this could work, really i do. but i can't help but wonder a bit.

Agreed, Zach. Research has shown sharks are color blind and rely on contrast and other signals, such as electric fields, to determine if something is predator or prey. If you notice in the video, they placed the fabric on chum buckets, which are submerged, usually close to the bottom. Not floating on the surface where humans (and real prey like seals) are. I'd be interested to see more of their research, though.